Motor fuels containing ether acids



United States Patent 3,416,901 MOTOR FUELS CONTAINING ETHER ACIDS George W. Eckert, Wappingers Falls, and Howard V.

Hess, Glenham, N.Y., assignors to Texaco Inc., a corporation of Delaware N0 Drawing. Filed Dec. 2, 1957, Ser. No. 699,942 10 Claims. (Cl. 4469) This invention relates to a hydrocarbon fuel composition of high octane rating. More specifically, it involves the discovery that the octane rating of leaded gasoline fuels is substantially improved by the addition of ether carboxylic acids.

The recent increases in compression ratios of automobile engines have placed a severe strain on petroleum refiners to produce fuels having the octane rating demanded by these engines. Premium fuels at the present time have research octane ratings between 97 and 100 and it has been predicted that premium fuels will have to have octane ratings between 105 and 110 five years from now in order to satisfy the octane requirements of the high compression automotive engines predicted for that date. In order to produce premium fuels of octane ratings of 95 and above, it has been necessary for refiners to rely heavily on catalytic refining operations such as fluid catalytic cracking, catalytic reforming, alkylation and catalytic isomerization.

Catalytic cracking and catalytic reforming, which are the most widely used refining operations in the production of high octane fuels, produce substantial quantities of aromatics; catalytic cracking also produces a substantial amount of olefins. It is well known that olefins and aromatics, although possessing high octane ratings, have a poorer response to organo-lead compounds such as tetraethyl lead than saturated aliphatic gasoline components. Accordingly, as the aromatic and olefinic contents of the gasolines have increased to meet the octane levels required by modern automotive high compression engines, the lead response of the resulting fuels has diminished. Stated another way, the octane increment obtainable by the addition of an organo-lead compound decreases as the aromatic and olefin contents of the base fuel increase. The subject invention involves the discovery that the octane rating of leaded motor fuels containing a substantial concentration of high octane components, that is, aromatics, olefins and mixtures thereof, is markedly improved by the addition of a small amount of an ether monocarboxylic acid.

In the copending application Ser. No. 689,466, filed Oct. 11, 1957, it is disclosed that monocarboxylic acids in prescribed concentration substantially raise the octane rating of -a motor fuel containing an organo-lead antiknock agent and a substantial concentration of high octane components which may be aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof. The subject invention involves the discovery that ether monocarboxylic acids exert a similar anti-knock action in motor fuel compositions of the prescribed type.

The high octane hydrocarbon motor fuel of this invention comprises high octane components including a substantial concentration of aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof, an organo-lead antiknock agent and an ether monocarboxylic acid in a concentration of at least 0.1 volume percent of fuel.

The action of ether monocarboxylic acids in raising the octane rating of gasoline is characterized by several unusual features. In the first instance, ether carboxylic acids appear to be ineffective in raising the octane rating 3,416,901 Patented Dec. 17, 1968 of gasolines unless an organo-lead anti-knock agent, normally tetraethyl lead, is a component of the gasoline mixture.

The second unusual characteristic of the action of ether monocarboxylic acids in appreciating the octane rating of gasolines is the fact that an equivalent concentration of acids appears to cause a greater octane improvement above the 100 octane level than below the 100 octane level.

The third unusual feature of the action of ether monocarboxylic acids is that they appear to have substantially no effect on the octane rating of a gasoline consisting essentially of saturated aliphatic hydrocarbons even though an organo-lead anti-knock agent is present. Since organolead anti-knock agents exert their greatest octane appreciation in predominantly saturated paraflinic base hydrocarbon gasolines and have the least effect on the octane rating of aromatic and olefin rich gasolines, the present invention neatly complements tetraethyl lead as an octane improver. Ether monocarboxylic acids have their minimum effects where tetraethyl lead has its maximum effeet and exert their maximum effect on octane values where tetraethyl lead has its minimum effect.

The novel fuel compositions of this invention have a minimum concentration of aromatic and/or olefin components of at least 10 volume percent. The aromatic and/ or olefin components of the motor fuel of the invention can constitute as high as 100 volume percent thereof but usually comprise between 20 and volume percent. The minimum 10 percent concentration is necessary for ether monocarboxylic acids to exert a significant octane improvement.

The aromatic components of the motor fuel of the invention are generally supplied by catalytic reforming or catalytic cracking operations. Catalytic reformate is particularly high in aromatics. The olefin components of the motor fuel of the invention are derived either from thermal cracking, catalytic cracking or. polymerization.

The organo-lead reagent necessary for the action of ether monocarboxylic acids as octane improvers is a tetraalkyl lead compound of the class known to possess anti-knock action. Tetraethyl lead is practically universally used as an -anti-knock agent but other tetraalkyl lead compounds such as tetramethyl lead, tetrabutyl lead, tetraamyl lead, tetrapropyl lead, etc. are known to possess anti-knock properties and may be usedin the fuel compositions of the invention in conjunctionwith ether monocarboxylic acids.

The tetraethyl lead mixtures commercially available for automotive use contain an ethylene chloride-ethylene bromide mixture as a scavenger for removing lead from the combustion chamber in the form of volatile lead halides. As used hereafter in the examples illustrating the invention, tetraethyl lead fluid denotes the commercial product which comprises tetraethyl lead, ethylene chloride and ethylene bromide, the latter two reagents being present in 1.0 theory and 0.5 theory, respectively, theory denoting the stoichiometric amount required for reaction with the lead content of the tetraethyl lead.

The organo-lead reagent is present in the fuel compositions of the invention in concentrations between 0.5 ml. per gallon up to the statutory limit of organo-lead reagent concentration which, at the present time, is 3 ml. per gallon in the case of automotive fuel and 4.6 ml. per gallon in the case of aviation fuel. The usual concentration of tetraethyl lead is between 1 and 3 ml. per gallon in automotive gasoline and 2 to 4.6 ml. per gallon in aviation gasoline.

Ether acids which are effective in increasing the octane rating of an aromatic and/or olefin-containing gasoline in the presence of an organo-lead anti-knock agent contain 330 carbon atoms and have the general formula: ROR'COOH wherein R is a monovalent hydrocarbyl radical containing 1-l8 and preferably 1-12 carbon atoms and R is a divalent hydrocarbyl radical containing 1-12 carbon atoms and preferably l-8 carbon atoms. Although both R and R can be aliphatic, cycloaliphatic or aromatic hydrocarbyl radicals, R is generally a divalent aliphatic hydrocarbyl radical and R is generally an aryl hydrocarbyl radical or an aliphatic hydrocarbyl radical. Preferred ether acids are alkoxy aliphatic monocarboxylic acids and aryloxy aliphatic monocarboxylic acids.

Examples of ether acids effective as octane improvers in the fuel compositions of the invention are methoxyacetic acid, ethoxyacetic acid, phenoxyacetic acid, tolyloxyacetic acid, 3-ethoxypropionic acid, Z-methoxypropionic acid, 2- ethoxy n-octanoic acid, 2-phenoxy n-hexanoic acid, 2- methoxy n-dodecanoic acid, 3-isopropoxy 2-ethylhexanoic acid, and ortho-ethoxybenzoic acid.

The effectiveness of ether-substituted monocarboxylic acids in raising the octane rating of leaded fuels containing an aromatic and/or olefin content is particularly surprising in view of the fact that other substituted monocarboxylic acids such as hydroxy monocarboxylic acids, halogenated monocarboxylic acids and sulfhydryl-substituted monocarboxylic acids are ineffective as anti-knock agents in the fuel compositions of the invention.

The ether monocarboxylic acids must be present in the leaded aromatic and/or olefin-containing compositions of the invention in a minimum concentration of 0.1 volume percent before a significant octane appreciation is realized. When the ether acid concentration is below 0.1 volume percent, no octane improvement is obtained in leaded gasoline containing at least 10 volume percent aromatics and/or olefins. The preferred concentration of ether monocarboxylic acid in the fuel compositions of the invention falls between 0.2 and 1.0 volume percent with maximum octane appreciation generally being obtained at a concentration level of about 0.5 volume percent. Concentrations of ether monocarboxylic acids as high as volume percent can be incorporated in the fuel compositions but no additional octane improvement is realized at the higher concentrations and economic considerations preclude the use of such concentrations in commercial fuel compositions.

In the following table there is shown the action of ether-substituted monocarboxylic acids in raising the octane rating of the leaded fuel compositions of the invention. The base fuel to which the ether acids were added in the concentration of about 0.5 volume percent was a catalytically reformed naphtha containing 3 cc. of tetraethyl lead fluid per gallon and having an IBP of 130 F. and an end point of 394 F. The base fuel had a leaded Research Octane Rating of 96.6 and an aromatic concentration of 48 volume percent as measured by Fluorescent Indicator Analysis (PIA) Method.

TABLE I Research Octane No.

Base fuel 96.6 Base fuel+0.5 v. percent methoxyacetic acid 98.0 Base fuel-+0.5 v. percent ethoxyacetic acid 98.1

Base fuel+0.5 v. percent mono-chloroacetic acid 87.0 Base fuel-{-05 v. percent heptafluoroacetic acid 89.3

Base fuel+0.5 v. percent 2-bromohexanoic acid 96.3 Base fuel-{-05 v. percent mercaptoacetic acid 96.0 Base fuel+0.5 v. percent ricinoleic acid 96.6 Base fuel+0.5 v. percent salicylic acid 96.6

The foregoing data demonstrate very clearly the effectiveness of the prescribed concentration of ether acids in raising the octane rating of a leaded gasoline having the prescribed aromatic content. The improvement in octane rating obtained by the addition of 0.5 volume percent methoxyacetic acid and ethoxyacetic acid is significant.

The data in the table also indicate the specificity of ether acids in raising the octane rating of leaded fuels containing an aromatic and/ or olefin content. While the ether acids effected better than a 1 unit improvement in research octane rating, the halogenated acids, hydroxy acids and mercapto acids either had no effect or substantially decreased the research octane rating of the leaded catalytic reformate.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing a tetraalkyl lead antiknock agent, substantial quantities of high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof and an ether hydrocarbyl monocarbox-ylic acid in an amount sufiicient to improve the octane rating of said hydrocarbon fuel.

2. A hydrocarbon fuel in the gasoline boiling range containing an organo-lead anti-knock agent, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons, and mixtures thereof in a concentration of at least 10 volume percent, and an ether hydrocarbyl monocarboxylic acid containing 3 to 30 carbon atoms, said ether acid being present in a concentration between 0.1 and 5.0 volume percent, said concentration being sufficient to effect substantial improvement of the octane rating of said hydrocarbon fuel.

3. A hydrocarbon fuel according to claim 2 in which said ether acid has the general formula: ROR'COOH in which R is a hydrocarbyl radical containing l-18 carbon atoms and R is a divalent hydrocarbyl radical containing 1-12 carbon atoms.

4. A hydrocarbon fuel according to claim 2 in which said organo-lead anti-knock agent is present in a concentration between 0.5 and 4.6 cc. per gallon.

5. A hydrocarbon fuel in the gasoline boiling range containing a tetraalkyl lead anti-knock agent in a concentration of at least 0.5 cc. per gallon, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in a concentration of at least 10 volume percent of said fuel and an ether acid of the general formula ROR'COOH in which R is a monovalent hydrocarbyl radical containing l-l2 carbon atoms and R is a divalent hydrocarbyl radical containing l-8 carbon atoms in a concentration of 0.1 to 5.0 volume percent.

6. A hydrocarbon fuel according to claim 5 in which the concentration of said ether acid is between 0.2 and 1.0 volume percent.

7. A hydrocarbon fuel according to claim 5 in which said high octane components constitute 20-80 volume percent of said fuel. 0

8. A hydrocarbon fuel according to claim 5 containing 1.0 to 4.6 cc. of tetraethyl lead per gallon.

9. A hydrocarbon fuel according to claim 5 in which said ether acid is methoxy acetic acid.

10. A hydrocarbon fuel according to claim 5 in which said ether acid is ethoxy acetic acid.

References Cited UNITED STATES PATENTS 1,692,784 11/1928 Orelup 6:31 44 66 2,210,942 8/1940 Lipkin 44-77 2,333,726 11/1943 Von Leibitz-Piwnicki- 260-535 2,667,408 1/1954 Kleinholz 4466X (Other references on following page) 5 6 FOREIGN PATENTS Improved Motor Fuels Through Selective Blending, 640 311 3/1928 France Wagner et al., paper presented before American Petro- France' ICUIII Institute, NOV. 7,

837,965 11/1938 France. 1,103,895 6/1955 France- DANIEL E. WYMAN, Primary Examzner.

277,326 1/1929 Great Britain, Y. H. SMITH, Assistant Examiner. 599,222 3/1948 Great Britain. Us CL OTHER REFERENCES 

1. A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE CONTAINING A TETRAALKYL LED ANTIKNOCK AGENT, SUBSTANTIAL QUANTITIES OF HIGH OCTANE COMPONENTS SELECTED FROM THE GROUP CONSISTING OF OLEFINIC HYDROCARBONS, AROMATIC HYDROCARBONS AND MIXTURES THEREOF AND AN ETHER HYDROCARBYL MONOCARBOXYLIC ACID IN AN AMOUNT SUFFICIENT TO IMPROVE THE OCTANE RATING OF SAID HYDROCARBON FUEL. 